How exactly SELECT query is processed internally after initial startup of Database?
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How exactly SELECT query is processed internally after initial startup of Database?
HI,
As soon as u enter any SQL query, internally three processes occur:-
1.in first process the syntax error is checked.
2. second process is called parsing,in this oracle check whether the table is existing or not then column are checked n all.Also variable's value are assigned in this step only.
3.In third step execution of the query will occur and result is represented.
Only when a DDL statement gets accessed each time of its accessing the data dictionary is made referenced to. Once a database gets started on a database server a memory area called as System Global Area also called as SGA in short gets allocated. Then one or more Oracle processes get started. After starting of the instance the database gets mounted by the instance for querying and further processing on the database. Also after starting of the instance the listener opens and establishes a communication pathway and this is through which users connect to database for further processing of select statement.
Hope this link will be useful to u
[url]http://www.adp-gmbh.ch/ora/concepts/sql_stmt.html#parse[/url]
its better to follw the provided link or any good matrial for the topic.
parse binds executes fetch
this is the sequence of execution of any statement